1. Field of the Invention
The present invention relates to a polyether-ester block copolymer and filaments formed therefrom.
More particularly, the present invention relates to a polyether-ester block copolymer useful for producing highly elastic, ionic dye-dyeable filaments having a high modulus of elasticity and a small permanent set and capable of maintaining the modulus of elasticity and the permanent set thereof substantially at the initial levels even after applying a dry or wet heat treatment thereto, and filament formed therefrom.
2. Description of the Related Art
It is known that rubbers and polyurethane resins are useful for forming elastic filaments. Those elastic rubber or polyurethane filaments are advantageous in that they have a high elastic recovery but disadvantageous in that they have an excessively high stretching property and a relatively poor resistance to heat and light.
Recently, polyether-ester block copolymers were developed and are now employed as an elastic resin material. These polyether-ester block copolymers are not satisfactory in that, when shaped into filaments, the resultant elastic filaments have a lower elastic recovery from elongation than the conventional polyurethane filaments. Nevertheless, the polyether-ester block copolymer has advantages in that the copolymer can be formed into filaments by a melt-spinning method and the resultant filaments exhibit a satisfactory elastic recovery from elongation at a small elongation rate.
The conventional polyether-ester block copolymer elastic filaments, in which the molecular chains are bonded through hard segment crystals in a different manner from the conventional polyurethane elastic filaments, are also disadvantageous in that they have a larger permanent set and a poorer elastic property than those of the conventional polyurethane elastic filaments.
Further, the conventional polyether-ester block copolymer elastic filaments are not dyeable by ionic dyes, and thus cannot be dyed with, for example, cationic dyes Although the conventional polyether-ester block copolymer elastic filaments can be dyed with disperse dyes, the resultant dyed filaments exhibit an unsatisfactory washing and light fastness.
To improve the elastic property of the polyether-ester block copolymers, Japanese Unexamined Patent Publication Nos. 59-45349 and 59-45350 disclose methods of enhancing the degree of crystallinity of the block copolymers by adding a crystal nucleating agent to the copolymers, but the improvements obtained by these methods with regard to the elastic property are not high enough, and thus the elastic property of the resultant filaments is still unsatisfactory. Especially, when the filaments are used to form a portion or a whole of a knitted fabric, the elastic property of the filaments is practically lost during the knitting procedure.
For an enhancement of the dyeing property, it is known that a polyethylene terephthalate can be copolymerized with a comonomer having a metal sulfonate radical, for example, sodium 5-sulfoisophthalate, and converted to a cationic dye-dyeable copolymer. Also, an attempt has been made to apply the above-mentioned dyeing property-enhancing method to the polyether-ester block copolymer. This attempt, however, was unsuccessful in that the metal sulfonate radical-containing comonomers have a very poor copolymerizing reactivity to the conventional polyether-ester block copolymers, especially when tetramethylene glycol is employed as an ingredient of the glycol component.
Accordingly, there is an urgent need for the provision of an improved polyether-ester block copolymer having a satisfactory elastic property and dyeing property, and filaments formed therefrom.